This application claims the priority of German Patent Document DE 101 34 086.9, filed Jul. 13, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for connecting two components by high fluid pressure, the components being pushed onto one another and then being pressed against one another by way of the high pressure, and a device for connecting two components by way of high fluid pressure, comprising a high-fluid-pressure generator by which a sliding assembly of the components pushed onto one another can be acted on by the fluid pressure in such a manner that the components bear against one another in a press fit.
A generic method and generic device are known from, for example, U.S. Pat. No. 3,977,068. In this case, a tubular component is pushed into a through-hole of a plate-shaped component with play, after which an expanding lance is inserted into the tubular component, by means of which lance the tubular component is, by high internal fluid pressure, plastically expanded in such a manner that it comes to bear against the inside of the through-hole of the plate-shaped component. The latter is likewise expanded in the region of the hole, but only within the limit of the material elasticity. After the high internal pressure has been released, the hole wall recovers elastically, so that a virtually permanent press fit results, in the hole region, between the tubular component and the plate-shaped component. The expanding lance is formed by a rod made of a rigid solid material, preferably steel, which has an axially extending pressure duct for guiding the pressure fluid. The axial pressure duct is a blind bore and opens, shortly before its end, into two ducts which branch off radially and have their outlets in the lateral surface of the rod. In the in-use position of the expanding lance, the outlets lie inside the region to be expanded of the tubular component. This region is sealed axially so as to be resistant to high pressure by two annular seals which are spaced from one another and are accommodated in two annular grooves let into the lateral surface of the rod.
As the expanding lance is inserted into a tubular component and, for reasons of strength, has to have a specific minimum cross section depending on the high pressure to be applied, the inner component must necessarily likewise have a minimum inside diameter. Applicability to inner components with a small inside diameter is thus not possible with the known art. Moreover, the necessity of inserting the expanding lance makes it a prerequisite that the inner component must be hollow. On account of the limited long-term strength of the expanding lance, in particular in the case of thinner examples, use of the lance in series production leads to a relatively expensive production process for the joint connection as a result of the frequent tool-changing owing to tool wear and the associated down-times.
An aspect of the invention is, therefore, to develop a method and a device to the effect that components can, in a relatively simple and controlled manner, be interconnected without any limitation with regard to the minimum size of an inside diameter of the components and with regard to the design of the inner component.
According to certain preferred embodiments of the invention, this aspect is achieved in that an outer component of the two components, the material of which has a yield point which is lower than that of an inner component of the two components, is plastically deformed by high-pressure action acting on the two components from outside, the inner component being elastically deformed, with regard to the method; and in that the deforming tool surrounds the sliding assembly at least at a site of the press fit to be produced, wherein the deforming tool has a pressure duct which, connected to the high-fluid-pressure generator, leads from outside into an impression of the tool, which receives the sliding assembly, and an outlet of the duct is located at the site of the press fit to be produced, and wherein a sealing arrangement is arranged on an inner side of the impression on both sides of the site of the press fit to be produced, which sealing arrangements seal this site axially in a high-pressure-tight manner, with regard to the device.
Owing to the fact that the deforming action comes from outside, the requirement for inserting an expanding lance into an inner component is dispensed with. The dropping of the expanding lance means that there are no problems for the production process for the joint connection between the two components with regard to stability either, that is to say, wear of the tool to be inserted. As a result of this, the regular costs for the production of the connection are at the same time reduced. Furthermore, the shape of the inner component is no longer dependent on a minimum cross section of the lance. The inner components can thus now be polygonal, tubular, unsymmetrical, bent a number of times or even made of solid material
The limited criteria for the controlled production of the joint connection are, on the one hand, the possibility of pushing the outer component onto the inner component and, on the other hand, the matching of the materials and, if appropriate, the wall thicknesses of the components to one another, so that, when acted on by pressure fluid, the outer component is deformed plastically and the inner component is deformed elastically. This is embodied in the existence of an extensively closed opening of the outer component, into or through which the inner component is pushed or inserted, and in the elastic recovery of the material of the inner component outwards against the plastically shrunk outer component after release of the fluid pressure. This gives rise to the press fit between the two components which is sought according to certain preferred embodiments of the invention and the strength of which can advantageously be matched to the application concerned by variable control of the level of the fluid pressure, so that all strengths of the press fit can be set selectively between non-detachability and detachability of the press fit occasioned as of a given axial mechanical tension or pressure or a torque, for example for overload protection.
The long-term strength of the device according to certain preferred embodiments of the invention is absolutely assured, as the solidity of the deforming tool can be selected freely depending on the method. The smallness of the outside diameter of the components is determined only by the constructional feasibility of sealing arrangements in terms of their miniaturization. In comparison with known generic methods, considerably smaller components can consequently be joined together.
Expedient developments of the invention emerge from the preferred embodiments. Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.